Thermodynamic modeling of motlen salt solutions with multivalent cations having multiple coordination numbers

多组分体系的热力学和相平衡模型在当今的工业中具有重要的意义。冶金和化学工业通常使用热化学软件包来模拟化学反应和相平衡，以进行工艺开发。 多组分多价盐体系广泛用于金属的生产和加工。 铝电解、难熔金属涂层、下一代核反应堆、用于钛生产的有前途的电解质都依赖于熔盐化学。多组分盐体系的热力学和相平衡建模包括将相的吉布斯能扩展为T、P和组成的函数，并找到全局能量最小值。吉布斯能函数的模型参数通过优化它们的值以最好地同时再现文献中发现的实验数据（焓、液相线等）来获得。参数形成数据库，模型用于预测多组分体系的相平衡和热力学性质。吉布斯自由能模型必须符合多组分熔体的离子结构（氧化态和离子配位），特别是对于复杂的氯氟化物熔体，如NaF-KF-NaCl-KCl-TiFx-TiClx（x=2，3，4）体系，它溶解了一些具有变价态阳离子的氧化物组分。拟议的项目包括开发模型和参数数据库，用于预测具有工业重要性的多组分相互盐体系的相平衡（液相线和共晶温度，稳定产品，蒸汽压）和热力学性质（活性，焓，Cp），并考虑到离子的配位数和氧化态随组成而变化的新奇性。 将为NaF-KF-NaCl-KCl-TiF 2-TiCl 2-TiF 3-TiCl 3-TiF 4-TiCl 4和AF-BeF 2-ThF 4-UF 3-UF 4-UF 6（其中A为碱金属）系统开发模型。固溶体和纯化合物也将被整合到模型中。对于液体溶液，Ti和U将具有几个配位数（4-8），并且它们与组成的相对稳定性将根据测量来校准。

Thermodynamic and phase equilibrium modeling of multicomponent systems is of great industrial importance nowadays. The metallurgical and chemical industries commonly use thermochemical packages to simulate chemical reactions and phase equilibria for process development. Multicomponent multivalent salts systems are widely used for the production and processing of metals. Al electrolysis, coating of refractory metals, the next generation of nuclear reactors, promising electrolytes for Ti production all depend on molten salt chemistry. The thermodynamic and phase equilibrium modeling of multicomponent salt systems consists in expanding the Gibbs energy of a phase as a function of T, P and composition and finding a global energy minimum. Model parameters of the Gibbs energy functions are obtained by optimizing their values to best reproduce simultaneously the experimental data found in the literature (enthalpy, liquidus, etc.). Parameters form a database and the models are used to predict phase equilibria and thermodynamic properties in the multicomponent system. The Gibbs energy models must agree with the ionic structure of the multicomponent melt (oxidation states and coordination of ions), especially for complex chloro-fluoride melts dissolving some oxide components with cations of variables valency as the NaF-KF-NaCl-KCl-TiFx-TiClx (x=2, 3, 4) system. The proposed project consists in developing models and databases of parameters for the prediction of phase equilibria (liquidus and eutectic temperatures, stable products, vapor pressures) and thermodynamic properties (activities, enthalpy, Cp) of multicomponent reciprocal salts systems of industrial importance, with the novelty of taking into account the coordination numbers and oxidation states of the ions as they changes with composition. Models will be developed for the NaF-KF-NaCl-KCl-TiF2-TiCl2-TiF3 -TiCl3-TiF4-TiCl4 and the AF-BeF2-ThF4-UF3-UF4-UF6 (where A is an alkali) systems. Solid solutions and pure compounds will also be integrated in the model. For the liquid solution, Ti and U will have several coordination numbers (4-8) and their relative stabilities with composition will be calibrated on measurements.